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3/9/09 Chemistry Notes Chapter 7 Electron Structure of the Atom Electromagnetic Radiation and Energy light is electromagnetic radiation all forms of electromagnetic radiation travel through space as waves that move at the speed of light: 3.0 x 10^8 m/s Light is characterized by wavelength and frequency Electromagnetic Spectrum Forms of electromagnetic radiation include: gamma rays, xrays, ultraviolet visible, infrared, microwaves, and radio waves Wavelength and frequency As wavelength increases, frequency decreases frequency is in units of cycles per second, 1/s or s^-1 Atomic Spectra when visible light passes through a prism, its components separate into a spectrum white light, such as sun light or light from a regular light bulb, gives a continuous spectrum colored light, such as that from a neon sign, gives only specific colors in what is called a line spectrum Bohr’s Model of the Hydrogen Atoms Niels Bohr, a student of Rutherford, studied the line spectra of the hydrogen atom to try to understand the electrons in the nuclear model of the atom Bohr came up with a planetary model, in which electrons orbit the nucleus in circular pathways His model was based on the idea that electrons and their energies are quantized: they can have only certain values. Bohr Model When the electron moves from a higher energy orbit to a lower-energy orbit, it loses energy equal to the difference in energy between the orbits The energy is released as a photon Deficiencies of the Bohr Model It explains only the hydrogen atom and its spectrum a more complex model was needed to describe all atoms in general However the Bohr model did give insight into the quantized behavior of the atom that was later better understood The Modern Model of the Atom in the modern model of the atom, electrons are described as existing in orbitals Orbitals are 3 dimensional regions in space where an electron is likely to be found